In the assessment of co-owner John Mara, the Giants last season were “broken’’ on offense but thus far in free agency have gone to great lengths to re-fortify a defense that finished No. 8 in the NFL. Late Saturday night they signed two players, cornerback Walter Thurmond and safety Quintin Demps, and along the way unquestionably improved their special teams anemic return game.

Thurmond, 26, figures to challenge for a starting job alongside Prince Amukamara and likely means the Giants will not be re-signing their unrestricted free agent Terrell Thomas. Of course, the cornerback position remains a fluid situation, with Dominique Rodgers-Cromartie arriving Sunday for a visit. It is hard to imagine the Giants have the salary cap space for the player called DRC – one of the better young cover corners in the league, someone who would instantly upgrade the secondary and come with a high, high price tag.

Thurmond, who agreed to a one-year deal for $3.5M, arrives from the best defense in the NFL, as he was mostly a slot cornerback for the Seahawks. He ranked fifth in the league in fewest yards allowed in the slot, according to Pro Football Focus. He joins a cornerback group that includes Trumaine McBride and Jayron Hosley. Thurmond last season was suspended four games for violating the NFL’s substance abuse policy. He’s only played in 20 games the past three seasons, as he was sidelined for much of 2011 and 2012 with a broken leg.

Demps, 28, is not only a solid safety in coverage but he’s a dangerous kickoff returner – something the Giants desperately need, as if David Wilson can return from neck surgery he probably won’t be returning many, or any, kickoffs. Demps last season for the Chiefs averaged 30.1 yards on kickoff returns, the third-highest average in the league.

The Giants are now well-stocked at safety, their deepest position. In addition to starters Antrel Rolle and Will Hill, Stevie Brown was re-signed coming off knee surgery. Brown is expected to be ready for training camp after missing the entire 2013 season. He did have a team-high eight interceptions in 2012. Cooper Taylor, entering his second season, adds to the depth at safety.